One known type of projector that projects a colored image on a projection surface is one which synthesizes, for example, red laser light (R), green laser light (G) and blue laser light (B), and projects it on a projection surface (for example, refer to Patent Literature 1). This projector is used in practice for a head-up display (HUD), for example. A head-up display is something that allows a driver to see a virtual image overlapping the scene ahead of the windshield of an automobile or the like by means of a combiner (translucent reflecting member) provided on the windshield reflecting toward the driver an image projected from a projector.
In such a projector, a plate-shaped diaphragm member is arranged on the optical path of the laser light to remove stray radiation of the laser light that causes decreased quality of the projected image. Stray light is laser light that advances along a different optical path than the optical path of the laser light for projecting the image. In the diaphragm member, an aperture (opening) which penetrates through the diaphragm member in the direction of thickness of the diaphragm member is provided. When the laser light passes through the aperture, the range of flux of the laser light is restricted by the aperture, thereby enabling removal of stray light of the laser light.